Hesitation after oil change. Maybe solved?!?
08-22-17, 04:52 AM
#16
Driver
Thread Starter
I don't understand, is it not universally understood that the issue is the knock sensors triggered by the valve stems. Oil passes through these for lubricantation and a change in weight and / or viscosity could easily cause them to move excessively triggerig the knock sensors. Hence why the issue pops up at oil changes. Am I correct that this issue only affects 2012 and under as 13 got the redesigned heads? If this issue only affects 2012 and under I don't buy the vvti theory. It seems like the issue within the heads is quite logical as this component was what was redesigned not the variable valve timing.
https://www.clublexus.com/forums/att...sb-0033-08.pdf
https://www.clublexus.com/forums/att...sb-0033-08.pdf
08-22-17, 07:30 AM
#17
Yeah, I would try to persue a warranty claim for the valve stem guides if your car qualifies. I'm not saying that this is the only reason why knock sensors wrongly engage but I don't see how carbon buildup on the vvti sensor would produce resonance that would trigger the knock sensors. It's takes metal to metal vibrations to do this. One of the reasons why when I was looking to buy a 460 I was only looking at 13's and up. Very expensive to replace the heads.
Last edited by Lexuslsguy; 08-22-17 at 07:34 AM.
08-22-17, 07:40 AM
#18
Lexus Fanatic
I don't understand, is it not universally understood that the issue is the knock sensors triggered by the valve stems.
Again, this issue crops up IMMEDIATELY after an oil change. In my case, it was within a few blocks of driving and then disappeared after a few days or several hundred miles. Then, the next oil change later - hesitation. This happened to me 3 times on three oil changes, before I sorted it out.
08-22-17, 07:49 AM
#19
If the vvti theory was correct don't you think Lexus would have some sort of documentation that points to this? I have never seen any. Also, why only 2012 and under? Lexus identified the issue within the heads not the vvti system. Also, correct me if I am wrong, the TSB was like a bandaid on an infection. All it did was try to program the computer to ignore the resonance vs fixing the actual problem.
- Check the condition of the spark plugs and valve guides.
- If one or more of the spark plugs has a brown residue on the porcelain and electrode, continue to the Repair Procedure.
- If the spark plugs appear normal, confirm the valve stem oil clearance is within specification.
Maximum Oil Clearance:
Intake: 0.08 mm (0.0031 in.) - Exhaust: 0.1 mm (0.0039 in.)
If greater than specification, continue to the Repair Procedure.
Last edited by Lexuslsguy; 08-22-17 at 08:04 AM.
08-22-17, 08:05 AM
#20
So why not look at the OBDII data and plot it?
Calculated engine load, TPS position, RPM, Engine Temp, Ignition Advance, and you may need special software but knock Detection/Spark retard, and cam shaft position data and bam you have the facts. If knock is detected and the spark retarded it would show up here. I looked at an old Camry just for this data. I also ran different fuel grades through looking at ignition advance curves under load. The ECU will tell you what is happening if you look there.
The vvti relies exclusively on oil pressure to adjust cams position. If the oil was failing, surely analysis would have shown this by now, yes? But it happens with fresh oil. Perhaps learned habits induce this. We need to read the white papers on engine management to know what the ECU is capable of. If it compensates cam timing due to controlled oil leaks and fresh oil has less leaks, it could explain this.
How long until the sluggish acceleration disappears? Three freeway trips?
Calculated engine load, TPS position, RPM, Engine Temp, Ignition Advance, and you may need special software but knock Detection/Spark retard, and cam shaft position data and bam you have the facts. If knock is detected and the spark retarded it would show up here. I looked at an old Camry just for this data. I also ran different fuel grades through looking at ignition advance curves under load. The ECU will tell you what is happening if you look there.
The vvti relies exclusively on oil pressure to adjust cams position. If the oil was failing, surely analysis would have shown this by now, yes? But it happens with fresh oil. Perhaps learned habits induce this. We need to read the white papers on engine management to know what the ECU is capable of. If it compensates cam timing due to controlled oil leaks and fresh oil has less leaks, it could explain this.
How long until the sluggish acceleration disappears? Three freeway trips?
Last edited by 2013FSport; 08-22-17 at 08:09 AM.
08-22-17, 08:22 AM
#21
You can log all you want via Techstream and the PDF linked above specifically notes data logging as part of the diagnostic.
http://carspecmn.com/ls460-and-ls600...g-andor-p2119/
- Connect Techstream unit and test drive the vehicle. Record all data duplicating the concern. Review the Knock Correct Learn Value, and the Ignition (IGN) Advance.
- If the Knock Correct Learn Value drops from 17.0 CA to below 12.0 CA, and the IGN Advance goes to a negative degree value while duplicating the concern, continue to step 3.
http://carspecmn.com/ls460-and-ls600...g-andor-p2119/
Last edited by Lexuslsguy; 08-22-17 at 08:28 AM.
08-22-17, 06:05 PM
#23
Driver
Thread Starter
I don't think they want to figure it out. There is money to be made. People are paying to replace heads and all types of things. Most of these cars are out of warranty. And a lot of owners wont even bat an eye at this website or do any type of internet research for that matter. This is good for business.
08-22-17, 08:17 PM
#24
Lexus Fanatic
I don't think they want to figure it out. There is money to be made. People are paying to replace heads and all types of things. Most of these cars are out of warranty. And a lot of owners wont even bat an eye at this website or do any type of internet research for that matter. This is good for business.
08-23-17, 09:38 AM
#25
Lexus Fanatic
I don't think they want to figure it out.
08-24-17, 05:10 AM
#26
Pole Position
Keep in mind that the vvti system doesn't just use oil pressure, the exhaust cams use an electric motor, rather than the oil supplied units.
As far as the failed head theory, I could see that causing this problem, but not just after an oil change. And there are very few people that I know of that have had to have their heads replaced. On this entire forum I can only think of two instances. If you're using a lot of oil, the car hesitates often and the plugs look suspicious? Yeah I'd say you need heads, if not? Then I'd say the problem is something else.
As far as the failed head theory, I could see that causing this problem, but not just after an oil change. And there are very few people that I know of that have had to have their heads replaced. On this entire forum I can only think of two instances. If you're using a lot of oil, the car hesitates often and the plugs look suspicious? Yeah I'd say you need heads, if not? Then I'd say the problem is something else.
04-14-18, 09:45 AM
#27
Driver School Candidate
I bought a LS460 a month ago with 76000 miles on it and took it on a 3,000 mile trip. It performed flawlessly, in fact I think this was the first car I actually LOVED driving. And then I changed the oil. Immediately after it was hesitating and at times not accelerating unless I put the pedal to the floor. I actually stopped on the side of the road to make sure I put in enough oil. It was at the top of the dipstick marker. I did notice the morning after I changed the oil that the engine sounded a little starved for oil for a few seconds and then it was fine. Of course I started it after the oil change the night before. After reading the Lexus forums related to this problem, I disconnected the battery for 10 minutes and took it for a test drive. My baby is back! Accelerates like it did before. My guess is the knock sensor(s) thought the noise was an engine knock and dialed back the power to save the engine and disconnecting the battery made it forget.
04-16-18, 11:42 AM
#28
As previously metntioned the "Italian Tune-Up" is what mechanics have been doing for years with the little old lady vehicles that only get up to 30mph going to church. This isn't unheard of with today's suburban/urban commuters that an engine doesn't get up to full operating temp on short drives. This can cause all kinds of issues in different systems. Take your vehicles out on a hard drive every now and then. People seem to be under the impression that an engine is harmed by higher RPMs; I would contend an engine that never sees 5k RPM is going to have issues. Drive them!
04-17-18, 07:56 AM
#29
First off I don't know if the Italian tune up or Texas tune up relates to the mystery LS460 after oil change hesitation problem at all. My car has never experienced it. In the 90's Volvo who I worked for came out with a suggested fix for catalytic converter smell and failed emissions testing. We were instructed to go to a road where speeds up to about 50 mph could be achieved safely. Now put the transmission in 1st gear and floor it and stay in 1st gear the whole way racing the engine to the redline. Keep driving at the redline till the fuel pump would cut out (this was a safety feature built into the system) the computer would recognize the too high rpm and just shut the power to the fuel pump. Now the rpms would drop and the fuel pump would start up again. Big on off bucking action. Anyway low and behold the cats would stop smelling like rotten eggs and I personally witnessed many cars pass emissions that had failed before doing this crazy procedure. Or you could always replace the cats at a big expense that warranty would not pay for.
04-17-18, 04:35 PM
#30
Lexus Fanatic
first off I don't know if the Italian tune up or Texas tune up relates to the mystery LS460 after oil change hesitation problem at all. My car has never experienced it.